Tube fitting assembly method

ABSTRACT

A malleable tube is assembled to a rigid fitting by placing the end of the tube over one end of the fitting which has a barb with a locking face facing away from the end of the fitting and a sloping face facing the end of the fitting, the tube is gripped with jaws which have an inward nose projection of a small axial extent and this nose projection grips the tube at about the end of the fitting, force is applied between the fitting and the jaws to relatively move the fitting and tube longitudinally into the jaws until the nose projection has relatively moved past the barb on the fitting.

BACKGROUND OF THE INVENTION

Tube and fitting assemblies have been devised in many differentstructures and methods of assembly. The usual case of a tube telescopedover a part of a fitting is where jaws of some kind have generallyradially compressed the tube into sealing contact with that part of thetelescoped tubing and fitting. In such case the tube is compressedradially inwardly to make the seal. This is difficult to actually make agood seal because the tube, even though malleable and has been deformedpast its elastic limit, tends to have a certain amount of elasticity andsprings back radially outwardly after the jaw pressure has been removed.Thus, in many cases the fluid seal between the tube and the fitting isdestroyed or at least lowered as to the fluid pressure it willwithstand.

SUMMARY OF THE INVENTION

The present invention is directed to a tube and fitting assembly andmethod of assembly wherein this radial expansion does not occur afterthe assembly pressure is removed and the assembly jaws move relativelylongitudinally along the tube to give compression thereof. Thislongitudinal relative movement causes the tube to bulge outwardly andbulge inwardly in front of the jaws during relative movement so that ifthere is any relaxation of the tube when the pressure is removed thisrelaxation is radially inwardly instead of outwardly. This assures atight seal which withstands pressure up to the bursting pressure of thetube.

Accordingly, an object of the invention is to make a tube fittingassembly by the method of moving jaws longitudinally relative to thetelescoped tube and fitting.

Another object of the invention is to provide one or more barbs on thefitting and a compression nose ring on the jaws so that a small annularportion of the tube is deformed inwardly and then the jaws are movedrelative to the tube and assembled telescope fitting in a longitudinaldirection so that the nose ring compresses the tube and moves a portionof it longitudinally to make a seal with the fitting.

Other objects and a fuller understanding of the invention may be had byreferring to the following description and claims, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a longitudinal cross sectional view of a tube telescoped overa part of a fitting ready for assembly;

FIG. 2 is a longitudinal sectional view of jaws with a nose ring clampedon a small portion of the tube;

FIG. 3 is a similar longitudinal sectional view with the fitting andtube moved longitudinally part way into the jaw nose ring;

FIG. 4 is a longitudinal sectional view of the completed assembly;

FIG. 5 is a longitudinal sectional view of a modified form of fittingwherein a knurl is provided for anti-rotation;

FIG. 6 is a longitudinal sectional view of the assembly method partlycompleted;

FIG. 7 is a longitudinal sectional view of the completed assembly; and

FIG. 8 is a longitudinal sectional view of another modification wherehelical threads are used.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The fitting and tube assembly method is disclosed in FIGS. 1-4 with FIG.4 illustrating the finished assembly except for removal of the jaws.FIG. 1 shows a typical fitting 11 and a tube 12 with the tube telescopedover a forward end 13 of the fitting. The fitting has one or a pluralityof barbs 14, in this case shown as two annular barbs. Each barb has asloping face 15 facing the forward end 13 of the fitting and has alocking face 16 facing away from the end 13. Further, the fitting has anabutment 18 which is a longitudinal abutment arresting movementlongitudinally of the tube 12 and has an annular surface 19, preferablya cylindrical surface contiguous to the abutment. The rear end 17 of thefitting may provide a wrench pad, such as a hexagonal surface. In thepreferred embodiment, at least one of the barbs is annular so that aseal may be obtained at that area between the tube and the fitting.

In FIG. 1 the tube may loosely telescope over the forward end 13 of thefitting or it may be a friction fit with the barbs actually scrapingalong the inside diameter of the tube.

FIG. 2 shows two jaws 21 and 22, each with an inward nose projection 23.Two or more jaws may be used and when clamped on to the tube as shown inFIG. 2 this inward nose projection on the jaws makes a substantiallyannular nose ring and this is annular except for the split between thejaws. The jaws also have a small forward extension 24 and a longerrearward extension 25. The forward extension 24 has preferably a smallclearance relative to the outside diameter of the tube and the rearwardextension 25 also has essentially the same amount of clearance relativeto the tube, for guiding the tube.

At this point longitudinal force is applied to start assembly. This maybe applied by moving the jaws longitudinally relative to a stationaryfitting, but is shown by force acting on a punch 29 brought against theend surface 30 of the fitting and, hence, longitudinal movement isprovided relatively between the punch and the jaws and also between thejaws and the fitting and telescoped tube. FIG. 3 shows the assemblymethod about half way completed where the jaws do not spring open asthis longitudinal relative movement is progressing so the metal of thetube, which is malleable, bulges radially outwardly at 31 ahead of theadvancing nose ring 23. The bulge 31 may be restrained the forwardextension 24 of the jaws. The relative longitudinal movement also causesthe malleable tube to flow generally radially inwardly against thesloping faces 15 of the barbs 14. The flowing metal caused by thislongitudinal relative movement causes the end of the tube 32 to bejammed against the abutment 18 and to be compressed radially inwardly atthe cylindrical surface 19 by the time the assembly method is completedas shown at FIG. 4. It has been found that a fluid tight seal isachieved at each of the barbs, at the abutment 18 and at the cylindricalsurface 19. This seal is established by the relative longitudinalmovement without any radial inward compression of the jaws as the jawsmove longitudinally relative to the punch 29. There is initial radiallyinward compression only at the nose ring 23. At least when thelongitudinal force is removed and the jaws being removed from the tube,any relaxation of the tube is an inward radial relaxation rather thanoutward radial relaxation as in the prior art. It has been found thatthe tube end 32 expands somewhat radially right adjacent the abutment 18and also is contracted radially inwardly into sealing engagement withthe cylindrical surface 19 due to the flow of metal of the malleabletube. It has been found that the tube and fitting seal will withstand1,000 PSI fluid pressure and in fact will make a tight seal up to thebursting pressure of the tube itself.

FIGS. 5, 6 and 7 show a modification of the invention. FIG. 5 is likeFIG. 2 with the jaws nose ring 23 clamped on the tube so that there is aradially inward bulge 33 to engage near the end of the fitting 51. Therear end 17 of the fitting may have the usual hexagonal wrench pad forholding or twisting the fitting, the same as in FIGS. 1-4.

FIG. 6 shows the assembly part way through where the nose ring hascaused inward flow of the tube metal against the barbs 14, caused theoutward bulge 31 in the tube ahead of the nose ring and caused theinward bulge 33 ahead of the nose ring.

In this embodiment an anti-rotation surface 34 is provided on thefitting between the inner most barb and the abutment 18. In FIGS. 5-7this is a knurled surface on a previously cylindrical, slightly enlargeddiameter portion of the fitting. The cylindrical surface 19 or neck isagain provided adjacent the abutment 18. Again, with FIG. 6 similar toFIG. 3, this shows the progressive inward and outward bulges justforward of the nose ring and in FIG. 7 with the final assembly movementcompleted, the tube has been jammed against the abutment and has made aseal there as well as at the neck 19 and at the barbs, or at least thetips of the barbs 14. Usually, a seal does not occur at the knurlsbecause the metal often does not flow enough inwardly to make a seal inthe trough of these knurls.

FIG. 8 is a modification wherein the barbs are formed by externalthreads 54. These barbs are therefore not annular but are helical. FIG.8 is like FIG. 7 showing the completed assembly with the jaws removed.It has been found that the tube does not flow radially inwardlysufficient to make seal at the thread barbs, instead the seal isprovided at the abutment 18 and at the cylindrical surface 19. Byholding the tube with some jaws which tightly grip the tube andrelatively rotating the fitting 52, it has been found that this assemblycan be unscrewed, and therefore, there are internal threads 55 formed onthe inside of the tube. This is a way to form threads without cutting orrolling on the I.D. of the tube.

In fittings which have been tested and constructed in accordance withthe invention of FIGS. 1-4, the barbs 14 have been annular barbs ofabout 0.015" to 0.030" larger radially than the cylindrical surface ofthe end of the fitting 17. For example, if the tube 12 used is 3/8"outside diameter, the commercial standard is ±0.004 of an inch and with0.032" of wall thickness. Such a tube and fitting assembly can withstandthe 2,800 psi bursting pressure of the tube. Even if a number offittings 11 are manufactured and all mixed together in one tote tray,this may put slight nicks in the barbs, but it has been found that thesenicks are filled in by the flow of the tube metal by the time thefitting assembly is complete as shown in FIG. 4. In any event, a seal ismade at the cylindrical surface 19 and also made at the abutment 18 sothat the totality of the seals prevents leakage up to the burstingpressure of the tube. For 1/8" O.D. tube, the commercial standardtolerance is ±0.002 with 0.028" wall thickness with a tolerance of±0.002. In this case, the barbs typically may be from 0.005 to 0.015" inradial extent. These are also dimensions which are true for themodifications shown in FIGS. 5-7. For the threaded variation in FIG. 8,this can be a standard thread which is not tapered. It may be, forexample, cut by a threading die into the fitting 52 by a standard dieset such as a 10-24 threading die.

The present disclosure includes that contained in the appended claims,as well as that of the foregoing description. Although this inventionhas been described in its preferred form with a certain degree ofparticularity, it is understood that the present disclosure of thepreferred form has been made only by way of example and that numerouschanges in the details of construction and the combination andarrangement of parts may be resorted to without departing from thespirit and the scope of the invention as hereinafter claimed.

What is claimed is:
 1. A method of assembling a malleable tube to arigid fitting, the fitting having an external surface with at least onebarb thereon, said at least one barb having a locking face facing awayfrom a forward end of the fitting and a sloping face facing the forwardend of the fitting, and the fitting having an abutment facing theforward end of the fitting and located rearward of the barb, and saidmethod comprising the steps of:placing the tube over the forward end ofthe fitting and the at least one barb and engaging the abutment;gripping the tube with jaws which have an inward nose projection of asmall axial extent at about the forward end of the fitting;longitudinally moving the fitting and the tube relative to the jawsuntil the nose projection has relatively moved past the at least onebarb; and guiding the tube with a rear portion of said jaws during thestep of relative longitudinal movement.
 2. The method as set forth inclaim 1, wherein the step of relative longitudinal movement includescompressing the tube longitudinally with the nose protection.
 3. Themethod as set forth in claim 2, wherein said longitudinal compression ofthe tube is ahead of the nose projection and causes the tube to moveradially inward against the fitting making a sealing area therebetween.4. The method as set forth in claim 3, wherein the sealing area is atleast one barb.
 5. The method as set forth in claim 3, wherein thesealing area is at an annular area rearward of the at least one barb. 6.The method as set forth in claim 1, wherein said relative longitudinalmovement causes the tube to expand radially outward ahead of the noseprojection.
 7. The method as set forth in claim 6, further comprisingthe step of restraining the outward expansion of the tube ahead of thenose projection with a forward portion of said jaws during the step ofrelative longitudinal movement.
 8. The method as set forth in claim 1,wherein said relative longitudinal movement causes the tube to moveinwardly with a radial component at places permitted by the shape of thefitting.
 9. The method as set forth in claim 1, wherein the jaw noseprojection is substantially annular.
 10. The method as set forth inclaim 1, wherein at least one barb is annular.
 11. The method as setforth in claim 1, including a non-cylindrical surface on said fittingand wherein the relative longitudinal movement moves the tube intoengagement with said non-cylindrical surface for anti-torque movementsof said tube and fitting.
 12. The method as set forth in claim 11,wherein said non-cylindrical surface is on one of said abutment, said atleast one barb, and at least a portion of said exterior surface.
 13. Themethod as set forth in claim 11, wherein said non-cylindrical surface isa knurled surface.
 14. The method as set forth in claim 1, wherein therelative longitudinal movement continues until the nose projection isadjacent the abutment.
 15. A method of assembling a malleable tube to arigid fitting, the fitting having an external surface at a forward endof the fitting, an abutment facing the forward end of the fitting andlocated rearward of the external surface, and a cylindrical surface at aforward side of said abutment and radially recessed from said externalsurface, said method comprising the steps of:placing the tube over theforward end of the fitting and the external surface and engaging theabutment; gripping the tube with jaws which have an inward noseprojection of a small axial extent at about the forward end of thefitting; longitudinally moving the fitting and the tube relative to thejaws until the nose projection is adjacent the abutment; longitudinallycompressing the tube ahead of the nose projection during the step ofrelative longitudinal movement to deform the tube radially inwardagainst the fitting; and forming a seal between the tube and one of saidabutment and said cylindrical surface.
 16. The method as set forth inclaim 15, further comprising the step of forming a seal between saidtube and at least one barb located on the external surface, said atleast one barb having a locking face facing away from the forward end ofthe fitting and a sloping face facing the forward end of the fitting.17. The method as set forth in claim 15, further comprising the step ofguiding the tube with a rear portion of said jaws during the step ofrelative longitudinal movement.
 18. The method as set forth in claim 15,further comprising the step of restraining an outward expansion of thetube ahead of the nose projection with a forward portion of said jawsduring the step of relative longitudinal movement.
 19. The method as setforth in claim 15, further comprising the step of engaging the tube witha non-cylindrical surface on said fitting during the step of relativelongitudinal movement to prevent relative rotation between the tube andthe fitting.
 20. The method as set forth in claim 19, wherein saidnon-cylindrical surface is on one of said abutment, at least one barblocated on the external surface, and at least a portion of said exteriorsurface.